Common Tiling Terms

There is a great deal of terminology used within the tiling industry. The following is a collection of the most common terms and their meanings.

Additive: Generally refers to a liquid polymer that can be added to a grout or adhesive to improve its adhesion and flexibility.

Adjusting time: The length of time after fixing a tile that it can still be adjusted without detriment to the adhesive bond strength.

Buttering: The process of spreading a thin layer of adhesive of the underside of textured tiles directly before bedding. This is to ensure a full bed of adhesive is achieved.

Calibrated / Un-Calibrated: A reference to the thickness of tiles. Calibrated tiles are manufactured to give a uniform depth so can be bedded onto adhesive using the same bed depth. Un-calibrated tiles are typically natural stone of varying thicknesses and require thicker bed depths.

Efflorescence: The appearance of light deposits of salts on cementitious materials, occasionally visible in grout lines. It is as a result of moisture bringing salts to the surface that when dry leave a white powdery deposit showing light and dark variations within the grout. It can occur due to moisture migration from the background substrate, by watering or premature cleaning off of the grout. It is not detrimental to grout performance.

Finished walls and floors: Prior to any tiling it is important that walls and floors are finished providing the level of smoothness and regularity required. This may be by means of rendering or plastering on walls or by use of a suitable smoothing compound on floors. A wall classed as finished and ready for tiling will have no greater than a 2mm deviation under a 2m straight edge. A finished floor, a 3mm deviation under a 3mm straight edge.

Fixing time: The length of time, after applying an adhesive, that tiles can be fixed.

Frost-resistant: The ability of a tile, adhesive or grout to perform even when the external conditions can result in frost formation. The tiles usually have to have very low water absorption to ensure cracking does not occur.

Grout after: Period after which the tiles are firmly set into the adhesive and will allow grouting to begin without disturbing the bond of the tile.

Internal / external: Products that are suitable for both internal and external use without affecting their performance parameters.

Laitance: A term used to describe a fine particle material deposit (often referred to as ‘fines’ or ‘fat’) found on the surface of cementitious or calcium sulphate subfloors. The deposit is a weak interface and should be removed to ensure the tile adhesive has a sound, strong surface to bond to. Laitance should be mechanically removed (often followed by vacuuming), and is caused by too much water when installing a screed. It can also be found when a levelling compound has been incorrectly used.

Movement joints: Gaps left in tiled floor designs and filled with a flexible material to enable the substrates and/or building to move independently of the tiling. Typically between different substrates, where tiles abut uprights, at corners and where expansion joints are present in the existing floor. Movement joints are essential design features.

Mould resistant: The ability of a product, usually a grout, to resistant the growth of mould.

Open time: The time, usually in minutes, after application of an adhesive within which it will still bond and secure the tile. This can be influenced by the nature of the substrate (with absorbent substrates reducing open time) and also the ambient conditions where warm, dry conditions reduce the open time.

Polymer modified: This term refers to adhesive and grout formulations that include added polymer for increased adhesion and flexibility. Polymer modified products are common due to the increased use of vitrified and porcelain tiles, which have a low absorbency and require a ‘better’ adhesive to adhere them.

Pot life: The length of time after mixing a grout or adhesive that you have to use it. After the pot life has been reached, the mixing product should be discarded. Water should not be added to try and regain its characteristics.

Primer: A liquid applied to a substrate prior to tiling. Used either to enhance adhesion or to reduce porosity providing a longer open time for the adhesive.

Rapid setting: An adhesive modified so it sets rapidly, by utilising different cements and technologies. Enables tiling and grouting to be carried out in a shorter time frame.

Ready mixed: Adhesives that are supplied ready for use, without the requirement to add any water or liquid polymer. Usually acrylic based and generally only used for wall tile installations where set time is not so critical.

Hard/Set time or ‘Workability’: The time, usually in hours, after which a bonded tile can be grouted and/or walked upon without affecting the bond. The set time for ready mixed adhesives is greatly dependent on the type of tiles and substrate.

Slump of slip: The vertical movement of a wall tile after it has been bedded into an adhesive. Traditionally battens have been used to prevent slump but modern adhesives are modified with anti-slump or anti-slip characteristics.

Solid bed fixing: A term used to describe a bed of adhesive or greater than 95% contact between tile back and adhesive, and between adhesive and substrate. This is recommended on all floor and large-format wall installations.

Tanking: Applying a liquid waterproof membrane, usually incorporating a mesh, in areas such as showers to protect moisture-sensitive background substrates from water impregnation.

Tensile adhesion strength: A standard test used to determine the adhesion strength of tiles and adhesive. Usually quoted in N/mm² the higher the number the greater the bond between the materials.

Tile after: This is the time after which the tiling process can start. Depending on the type of application being used, priming is generally the first stage.

Tile backer boards: These boards can be constructed from a variety of materials including cement, insulation, or resin based compounds reinforced to give added strength. These boards usually offer waterproofing and/or insulation properties.

Uncoupling membranes: These are membranes used below new tiling installations and generally fixed directly to the floor screed to prevent known problems in the subfloor affecting the new tiling installation.  By creating a separation layer between the tiles and the screed can effectively overcome substrate movement tensions, and stress crack issues.  They can also be used to provide waterproof protection neutralising vapour pressure build-up in problematic, as well as damp screeds.  They can be used above underfloor heating systems.

Underfloor heating: There are two basic types of underfloor heating systems.  The first uses warm water pipes either encased within the floor screed or fixed into pre-formed insulation panels.  Once positioned, installed, and commissioned the floor covering can be installed.  Hot water piped through the system provides the heating.  The second system uses electrical heating mats placed on to the prepared floor and connected to wall-mounted thermostatic controls.  Once commissioned the floor covering is installed.

Waterproof: The ability of an adhesive or grout to prevent the passage of water. Normally epoxy or resin materials, are often also chemically resistant.

Water repellent: Used usually when referring to grout, the product can repel water from its surface. Does not imply a waterproof grout.

Water resistant: The ability of an adhesive or grout to still retain its performance even when subject to fill immersion in water.

Water staining: A situation where moisture from adhesives and grouts gets into natural stone and dissolves existing materials resulting in discoloration. usually of the edges, but sometimes the faces of the tile. The use of rapid set products minimizes this risk, as does dealing with tiles prior to grouting.

Working time or ‘Workability’: The time, usually in minutes, after mixing an adhesive or grout that will still retain its characteristics to enable it to be applied, bedded onto, and finished. With rapid-set products, the working time will be reduced the longer the material is left in the mixed container. Also, warmer temperatures will reduce the working time.


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